System and method for controlling administration of medical fluid

ABSTRACT

A system for controlling administration of medical fluid includes a fluid passageway to which is attached a first flow regulator, a second flow regulator, and a flow detector. The system also includes a controller for controlling the first and second flow regulators in response to a measurement taken by the flow detector of fluid movement in the fluid passageway. The first flow regulator, such as a pump, is configured to maintain fluid movement at flow values greater than an unrestricted flow value. The second flow regulator, such as a variable adjustable valve, is configured to maintain fluid movement at a flow value less than the unrestricted flow value. A method of controlling administration of medical fluid includes obtaining a target flow value, moving fluid through the disposable assembly, taking a measurement of fluid movement in the disposable assembly, and actuating a flow regulating apparatus.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/481,609, entitled “SYSTEM AND METHOD FOR CONTROLLING ADMINISTRATIONOF MEDICAL FLUID, filed May 25, 2012, which is a continuation of U.S.application Ser. No. 11/414,794, entitled “SYSTEM AND METHOD FORCONTROLLING ADMINISTRATION OF MEDICAL FLUID, filed May 1, 2006, now U.S.Pat. No. 8,211,054, both of which are expressly incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the controlled administration ofmedical fluid and, more particularly, to intravenous fluid deliveryimplementing a control loop to achieve and automatically maintain adesired delivery parameter.

2. Description of the Related Art

Intravenous (“IV”) fluid delivery systems are used to deliver medicalfluid to patients at controlled rates. Many such IV fluid deliverysystems exist and in one case, precise infusion pumps have beendeveloped to more accurately provide medical fluids to patients inaccordance with physician prescriptions. In most cases, an open-looppump control system is used in which a processor varies the speed of afluid pump based on a predefined function of various parameters, such asfluid type, infusion profile, and programmed flow rate. Suchprocessor-controlled, open-loop pump systems can be expensive and areusually complex in that they are highly engineered with close toleranceparts to produce the desired accuracy of fluid delivery.

In most cases, such open-loop pumps do not use any feedback to alter thecontrol over the pumping mechanism. Sensors in the pump or associatedwith the fluid delivery are usually used to detect alarm conditionsassociated with peripheral events, such as an excessive amount of air inthe fluid delivery line, occlusion of the fluid tubing above or belowthe pump, and depletion of medical fluid in the container. The highlyengineered pumping mechanism and processor control accounts for almostthe entire accuracy of the pump. However, the rate of fluid delivery isalso affected by the precision of disposable components, such as thetubing, used in the fluid path that conveys the medical fluid to apatient. Variations in the internal diameter and material hardness oftubing and pumping components comprising the disposable componentscannot be readily compensated in an open-loop control algorithm sincesuch variations may change with the age of the component and since it isimpractical to measure such variations directly. As a result, disposablecomponents subject to tight tolerance specifications must be used insuch open-loop systems to ensure accuracy of fluid delivery. The tighttolerance specifications increase manufacturing costs which areultimately borne by the patient.

Certain closed-loop systems have been disclosed in the art over theyears and seek to maintain or increase medical fluid delivery accuracy.In a closed-loop system, a parameter or parameters associated with thefluid delivery process are measured to control the fluid deliverysystem. Prior closed-loop systems have often determined the flow rate ofmedical fluid to the patient by indirect means, such as by measuringinternal pressure forces on the wall of a fluid passageway or bymeasuring a fluid pressure gradient across a constriction in the fluidpassageway. Some prior systems have attempted to measure actual movementof the fluid in the fluid passageway; however, some such systems wereinvasive in that they involved physical contact with the medicinal fluidand were not implemented. Others required sensors and processing systemsthat were expensive and also were not implemented.

Fluid delivery manufacturers strive to provide a high level of fluiddelivery accuracy while at the same time strive to control costs topatients. A closed-loop pump system and method could provide usefulinformation about the actual delivery of fluid to the patient and ifaccurate enough, the pump device itself and disposable administrationcomponents could be manufactured with looser tolerances thereby reducingcosts to the patient. Such accuracy would enable manufacturers toprovide different means for delivering medical fluids to patients,including a reliance, at least partially, on gravity as the force tocause the fluid to flow to the patient.

Hence, those skilled in the art have recognized a need for a moreadvanced medical fluid delivery system and method using a sensor orsensors that measure actual fluid flow to the patient and use suchsensed flow information to regulate the fluid delivery. Those skilled inthe art have also noted a need for a lower cost fluid deliveryapparatus, including a flow regulator and flow conduits, having loosertolerances on parts so that costs are more controlled. Accordingly, itis desirable to provide a lower cost, less complex system for deliveryof medical fluids that reduces costs yet provides accuracy in fluiddelivery. The present invention satisfies these and other needs.

SUMMARY OF THE INVENTION

Briefly and in general terms, the present invention is directed to asystem and method for providing accurate medical fluid delivery to apatient using flow regulators and a flow sensor to determine the actualflow of the medical fluid to the patient so as to allow for control theflow regulators.

In an aspect of the present invention, a fluid control system forcontrolling administration of fluid from a medicament containercomprises a fluid passageway comprising an inlet, an outlet, and aninternal volume through which unrestricted movement of fluid correspondsto an unrestricted flow value, a first flow regulator attached to thefluid passageway and configured to keep fluid movement in the fluidpassageway at a flow value greater than the unrestricted flow value, asecond flow regulator attached to the fluid passageway and configured tokeep the fluid movement in the fluid passageway at a flow value lessthan the unrestricted flow value, a flow detector attached to the fluidpassageway and configured take a measurement of the fluid movement inthe fluid passageway, and a controller removably attached to the fluidpassageway and coupled to the flow detector, the first flow regulator,and the second flow regulator, the controller configured to control thefirst and second flow regulators in response to the measurement by theflow detector.

The first flow regulator in detailed aspects of the invention comprisesa pump chamber having a moveable wall coupled to a pump driver, the pumpchamber disposed in the fluid passageway and configured for one-wayfluid flow in a direction from the inlet to the outlet of the fluidpassageway, the pump driver comprising an elastomeric dielectric filmhaving a first side and a second side, the first side coated with afirst expandable conductive film connected to a first electrode, thesecond side coated with a second expandable conductive film connected toa second electrode, the dielectric film configured to expand in responseto a voltage applied to the first and second electrodes.

The second flow regulator in detailed aspects of the invention isfurther configured to keep the fluid movement in the fluid passageway ata flow value equal to the unrestricted flow value. In yet other detailedaspects, the second flow regulator comprises a variably adjustable valveconfigured to restrict the fluid movement in the fluid passageway.

The flow detector in detailed aspects of the invention comprises a heatsource disposed outside the internal volume of the fluid passageway andadapted to heat fluid located at a heating region in the fluidpassageway, a light source disposed outside the internal volume of thefluid passageway and adapted to produce an interrogating light directedtoward fluid located at an interrogating region in the fluid passageway,a light detector disposed outside the internal volume of the fluidpassageway and adapted to detect optical characteristics of the fluid inthe interrogating region, and to detect changes in the opticalcharacteristics when the heated fluid from the heating region enters theinterrogating region.

In another aspect of the present invention, a method of controllingadministration of fluid from a medicament container comprises obtaininga target flow value, moving fluid through a disposable assemblycomprising a fluid passageway and a flow regulating apparatus, the fluidpassageway comprising an inlet, an outlet, and an internal volumethrough which unrestricted movement of the fluid corresponds to anunrestricted flow value, the flow regulating apparatus comprising afirst flow regulator and a second flow regulator, taking a measurementof fluid movement in the fluid passageway, and actuating the flowregulating apparatus when the fluid movement does not correspond to thetarget flow value, including changing the operational status of thesecond flow regulator when the target flow value is less than theunrestricted flow value, and changing the operational status of thefirst flow regulator when the target flow value is greater than theunrestricted flow value.

Actuating the flow regulating apparatus, in detailed aspects of theinvention, includes changing the operational status of the second flowregulator when the target flow value is equal to the unrestricted flowvalue. In other detailed aspects, actuating the flow regulatingapparatus comprises actuating the flow regulating apparatus when thereis a change in the amount of fluid in the medicament container or achange in elevation of the medicament container relative to an outlet ofan administration tube extending from the outlet of the fluidpassageway. In yet other detailed aspects, actuating the flow regulatingapparatus comprises applying a voltage to a first electrode and a secondelectrode, the first electrode connected to a first expandableconductive coating on a first side of an elastomeric dielectric film,the second electrode connected to a second expandable conductive coatingon a second side of the elastomeric dielectric film, the elastomericdielectric film coupled to a moveable wall disposed on the fluidpassageway and configured to expand in response to the applied voltage.

Taking a measurement of fluid movement in the fluid passageway, in otherdetailed aspects, comprises heating fluid in a heating region in thefluid passageway, the fluid heated with a heat source disposed outsidethe internal volume of the fluid passageway, illuminating fluid in aninterrogating region in the fluid passageway, the fluid illuminated witha light source disposed outside the internal volume of the fluidpassageway, detecting optical characteristics of the fluid in theinterrogating region, the optical characteristics detected with a lightdetector disposed outside the internal volume of the fluid passageway,and detecting changes in the optical characteristics, the changesdetected with the light detector.

In another aspect of the present invention, a fluid control system forcontrolling administration of fluid from a medicament containercomprises a primary fluid inlet, a pump chamber in fluid communicationwith the primary fluid inlet, the pump chamber comprising a moveablewall and a pump outlet, the pump chamber configured for one-way fluidflow from the primary fluid inlet to the pump chamber and for one-wayfluid flow from the pump chamber to the pump outlet, a pump drivercoupled to the moveable wall of the pump chamber and configured to movethe moveable wall in response to a pump signal, a flow restrictor influid communication with the pump outlet, the flow restrictor comprisinga restrictor outlet and configured to selectively increase and decreasefluid flow through the restrictor outlet, a restrictor driver connectedto the flow restrictor and configured to actuate the flow restrictordevice in response to a restrictor signal, a flow detector comprising afluid conduit disposed between the flow restrictor and the pump chamber,the flow detector configured to produce and detect a thermal change influid in the fluid conduit and to provide a detector signalrepresentative of an existing fluid flow rate in the fluid conduit, auser input device configured to obtain a target flow rate from a user,and a controller in communication with the pump driver, the restrictordriver, and the flow detector, the controller configured to produce thepump signal and the restrictor signal to adjust the existing fluid flowrate to the target fluid flow rate and to automatically maintain theexisting flow rate at the target fluid flow rate.

In detailed aspects of the invention, the fluid control system comprisesa disposable assembly and a reusable assembly attached to the disposableassembly, the reusable assembly configured to be detached from thedisposable assembly, the reusable assembly comprising the controller andthe user input device, a display configured to communicate a flow rate,and a power source, the disposable assembly comprising the primary fluidinlet, the pump chamber, the pump driver, the flow restrictor, therestrictor driver, and the flow detector.

The flow restrictor in detailed aspects of the invention comprises amanual adjustment device connected to the flow restrictor device, themanual adjustment device sized to be manipulated by the user andconfigured to change movement of fluid through the restrictor outlet.

The pump driver in detailed aspects of the invention comprises a firstdiaphragm comprising a first elastomeric dielectric film disposedbetween a first pair of expandable conductive coatings and a seconddiaphragm comprising a second elastomeric dielectric film disposedbetween a second pair of expandable conductive coatings, the first andsecond diaphragms coupled to the moveable wall of the pump chamber, thefirst diaphragm configured to move the moveable wall in a firstdirection in response to voltage applied to the first pair of coatings,the second diaphragm configured to move the moveable wall in a seconddirection in response to voltage applied to the second pair of coatings.In other detailed aspects, the pump driver comprises a piezoelectricdevice coupled to the moveable wall of the pump chamber, thepiezoelectric device configured to move the moveable wall in response toa voltage applied to the piezoelectric device.

The detector signal from the flow detector, in detailed aspects of theinvention, represents a time period in which the thermal change travelsa predetermined distance in the fluid conduit of the flow detector.

The flow detector in detailed aspects of the invention comprises a heatsource disposed outside an internal volume of the fluid conduit of theflow detector, the heat source adapted to heat fluid in a heating regionin the fluid conduit, a light source disposed outside the internalvolume and adapted to produce an interrogating light directed towardfluid in an interrogating region in the fluid conduit, a light detectordisposed outside the internal volume and adapted to detect opticalcharacteristics of the fluid in the interrogating region, and to detectchanges in the optical characteristics when the heated fluid from theheating region enters the interrogating region. In more detailedaspects, the heat source is an optical device.

The features and advantages of the invention will be more readilyunderstood from the following detailed description which should be readin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system for controlling the administrationof fluid showing a fluid passageway to which is connected a fluidsource, a first flow regulator, a second flow regulator, a flowdetector, and a fluid administration tube, wherein the first and secondflow regulators and the flow detector being in communication with acontroller;

FIG. 2 is a cross-sectional side view of another system for controllingthe administration of fluid showing a fluid passageway to which isconnected a pump, a variably adjustable valve, a flow detector, acontroller, a knob, a display, and a power source, wherein the pumpcomprises a pump chamber in the fluid passageway and a moveable walladjacent the pump chamber, the moveable wall in contact with a platecoupled to a clamp of a pump driver, the pump chamber having two holesin which are located floating members of a first and a second checkvalve;

FIG. 3 is a perspective cross-sectional view of the pump driver of FIG.2 showing a first and second diaphragm having edges and middle portions,the edges spatially separated by a housing and the middle portions heldin closer proximity to each other by the clamp;

FIG. 4 is a cross-sectional detail view of the pump driver of FIG. 2showing the first diaphragm expanded such that the clamp, the plate, andthe moveable wall of the pump chamber are displaced in a first directionso as to increase the pump chamber in volume and draw fluid into thepump chamber through the first check valve;

FIG. 5 is a cross-sectional detail view of the pump driver of FIG. 2showing the second diaphragm expanded such that the clamp, the plate,and the moveable wall of the pump chamber are displaced in a seconddirection so as to decrease the pump chamber in volume and expel fluidout of the pump chamber through the second check valve;

FIG. 6 is a cross-sectional detail view of the flow detector of FIG. 2showing a heat source, a light source, and a light detector, each ofwhich is disposed outside an internal volume of the fluid passageway,wherein the heat source comprises a first laser device that heats fluidin a heating region in the fluid passageway, the light source comprisesa second laser device directed toward fluid in an interrogating regionin the fluid passageway, and the light detector comprises a photodiodein optical communication with the fluid in the interrogating region;

FIG. 7 is a cross-sectional side view of another system for controllingadministration of fluid showing a reusable assembly detached from adisposable assembly, wherein the reusable assembly comprises a display,a power source, a knob, and a controller, and the disposable assemblycomprises a fluid passageway to which is attached a pump, a flowdetector, and a variably adjustable valve;

FIG. 8 is a front view of yet another system showing a primary fluidinlet in fluid communication with a secondary fluid inlet;

FIG. 9 is a flow diagram of a method of controlling the delivery offluid showing automatically changing the operational status of a firstand a second flow regulator based on a comparison of a target flow valueto a measurement of fluid movement and to an unrestricted flow value,the operational status changes also being made automatically in responseto changes in the amount of fluid in a fluid source and changes in therelative elevation of the fluid source; and

FIG. 10 is a flow diagram of another method of controllingadministration of fluid showing comparing a target flow value to ameasurement of fluid movement, comparing a target flow value to theunrestricted flow value, determining the operational status of a firstand a second flow regulator, and, based on a result of thedetermination, incrementally changing pumping activity in a first flowregulator or incrementally moving a second flow regulator to a more openor more closed position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now in more detail to the exemplary drawings for purposes ofillustrating embodiments of the invention, wherein like referencenumerals designate corresponding or like elements among the severalviews, there is shown in FIG. 1 a block diagram of a system 20 forcontrolling administration of fluid from a medicament container or fluidsource. The system includes a fluid passageway 22 through which fluidflows. Attached to the fluid passageway is a first flow regulator 24, asecond flow regulator 26, and a flow detector 28. As will be describedin greater detail below, the flow detector 28 is configured to take ameasurement of actual fluid movement in the fluid passageway. Removablyattached to the fluid passageway is a controller 30 configured tocontrol the first and second flow regulators in response to themeasurement by the flow detector.

The fluid passageway 22 has an inlet 36 to which a fluid source 32 maybe connected and an outlet 38 to which an administration tube 34 may beconnected or at which an administration tube forms a part. One exampleof a suitable fluid source is an intravenous (IV) bag that contains amedical fluid. When the system 20 is in use, the administration tube 34is connected to a patient intended to receive the medical fluid. Thefluid passageway 22 has an internal volume configured to allow movementof fluid therethrough. Fluid movement may be restricted by a valve orother adjustable device attached to the fluid passageway. Unrestrictedfluid movement through the internal volume of the passageway correspondsto an unrestricted flow value. For example, when a valve or otheradjustable device attached to the fluid passageway is in a fully openposition, gravity induces fluid movement so that a volume of fluid flowexits the outlet 38 of the fluid passageway over a period of time. Inthis case, the unrestricted flow value may be represented by a flow ratein terms of milliliters per hour (ml/hr). It will be appreciated thatthe flow value may be represented in other terms, such as mass andweight.

Still referring to FIG. 1, the first flow regulator 24 is configured tokeep fluid movement in the fluid passageway at a flow value that isgreater than or equal to the unrestricted flow value. The first flowregulator may actively induce fluid movement through the passageway. Oneexample of a suitable first flow regulator is a pump. One embodiment ofsuch a pump includes an oscillating member that alternately draws fluidfrom the fluid source 32 and forces the drawn fluid through theadministration tube 34. In one embodiment, the pump produces a negativepressure to draw the fluid from the upstream medical fluid container andproduces a positive pressure to expel fluid to the administration tube34. It will be appreciated that fluid movement may be induced by thefirst flow regulator through the use of other types of devices known inthe art, such as a peristaltic pump. Preferably, the first flowregulator allows fluid movement at the unrestricted flow value when itis not actively inducing fluid movement.

The second flow regulator 26 is configured to keep fluid movement in thefluid passageway 22 at a flow value less than or equal to theunrestricted flow value. Preferably, the second flow regulator functionsas a flow restrictor capable of maintaining the flow value less than orequal to the unrestricted flow rate without the continuous or cyclicalconsumption of power. The second flow regulator may reduce fluidmovement by introducing an obstruction in the fluid passageway, and mayincrease fluid movement by withdrawing the obstruction. One example of asuitable second flow regulator is an adjustable valve having a moveablevalve member that extends into the internal volume of the fluidpassageway or pinches a resilient portion of the fluid passageway. Itwill be appreciated that fluid movement may be reduced or increased bythe second flow regulator through the use of other types of devicesknown in the art, such as a butterfly valve.

In the illustrated embodiment of FIG. 1, the first flow regulator 24,the second flow regulator 26, and the flow detector 28 are arrangedsequentially along the fluid passageway 22, with the first flowregulator 24 disposed closest the fluid source 32. It will beappreciated that the sequential order of these elements may be changed.

In FIG. 2 there is shown a cross-section of an embodiment of anothersystem 20. A fluid passageway 22 extends longitudinally from a primaryfluid inlet 36 to a primary fluid outlet 38. Adjacent and downstreamfrom the primary fluid inlet is a first flow regulator 24, in this casea pump 40. Adjacent and upstream to the primary fluid outlet is a secondflow regulator 26 that comprises a variably adjustable valve 42 in thiscase. A flow detector 28 is disposed between the pump and the variablyadjustable valve.

The pump 40 includes a pump chamber 44 in the fluid passageway 22 andis, thus, in fluid communication with the primary fluid inlet 36. Thepump chamber includes a moveable wall 46 and a pump outlet 48. The pumpchamber also includes a first check valve 50 arranged to ensure one-wayfluid flow from the primary fluid inlet to the pump chamber, and asecond check valve 52 arranged to ensure one-way fluid flow from thepump chamber to the pump outlet. The first and second check valves aredisposed sequentially within the internal volume of the fluidpassageway, with the first check valve disposed closest to the primaryfluid inlet.

The first and second check valves 50, 52 include a first floating member54 and a second floating member 56, respectively. The first and secondfloating members are sized and shaped to move freely within respectiveholes in a wall of the pump chamber 44. The first floating member isarranged such that it moves to an open position when fluid pressure inthe pump chamber is lower than fluid pressure in the primary fluid inlet36. The second floating member is arranged such that it moves to an openposition when fluid pressure in the pump chamber is greater than fluidpressure in the pump outlet 48. Although the check valves of theillustrated embodiment includes T-shaped floating members, it will beappreciated that one-way fluid flow may be achieved with other types ofcheck valves known in the art, such as ball-type valves. In any case,the check valves are preferably configured to allow fluid movement atthe unrestricted flow value when the pump 40 is not actively inducingfluid movement.

Still referring to FIG. 2, the moveable wall 46 of the pump chamber 44is physically coupled to a pump driver 58. The pump driver 58 comprisesa first diaphragm 60 and a second diaphragm 62 that are spatiallyseparated by a driver housing 64. The housing keeps edges of the firstand second diaphragms from moving. The first and second diaphragms havemiddle portions that are coupled together by a clamp 66. The clamp pullsthe middle portions together such that the first and second diaphragmsexert a biasing force on each other, such that movement of either one ofthe diaphragms is resisted by the other diaphragm. The clamp isconnected to a plate 68 in contact with the moveable wall 46 of the pumpchamber 44.

As shown schematically in FIG. 2, the controller 30 may be connected toa wireless communication device 31, which would communicate with awireless network 33 via radio frequencies 35 or other wireless meansknown in the art. The network may be part of an existing hospitalinformation system OM) 158. The wireless communication device allows aset of drug delivery data to be downloaded or received from the networkto the system 20. Such received data includes, but is not limited to,safety limits for checking drug delivery parameters subsequently enteredinto the system and an infusion program comprising several drug deliveryparameters. The wireless communication device also allows another set ofdrug delivery data to be uploaded or transmitted from the system to thenetwork. Without limitation, such transmitted data includes infusionstatus indicating the progress of drug delivery, alarm informationindicating a problem or potential problem with drug delivery, and drugdelivery information used for an electronic medical administrationrecord (eMAR), such as a drug identification, drug delivery start andcompletion times, a drug delivery flow rate, and other information.

In FIG. 3 there is shown a perspective cross-sectional view of the pumpdriver 58 of FIG. 2. The middle portions of the first and seconddiaphragms 60, 62 have holes, one of which is indicated by numeral 65,which align with holes in the clamp 66, one of which is indicated bynumeral 67. The holes allow air pressure on each side of the clamp toequalize while the clamp moves back and forth. A nut and bolt holdsportions of the clamp together. The bolt is connected to the plate 68(FIG. 2).

Referring to FIGS. 4 and 5, the pump 40 regulates fluid movement in thefluid passageway 22 when the pump driver 58 moves the moveable wall 46to alternatively increase and decrease the volume of the pump chamber44. When the pump chamber volume is decreased (from FIG. 4 to FIG. 5),fluid pressure in the pump chamber increases relative to fluid pressuresat the primary fluid inlet 36 and the pump outlet 48. The pressureincrease causes the first check valve 50 to close and the second checkvalve 52 to open, thereby expelling fluid from the pump chamber to thepump outlet. Subsequently, when the pump chamber volume is increased(from FIG. 5 to FIG. 4), fluid pressure in the pump chamber decreasesrelative to fluid pressures at the primary fluid inlet and the pumpoutlet. The pressure decrease causes the second check valve to close andthe first check valve to open, thereby drawing fluid from the primaryfluid inlet to the pump chamber.

Referring to FIGS. 2-5, the first diaphragm 60 comprises anelectroactive polymer in the form of an elastomeric dielectric polymerfilm in this embodiment. The film has a first side and a second side.The surface of the first side is coated with a first expandableconductive film electrically connected to a first electrode (not shown).The surface of the second side is coated with a second expandableconductive film electrically connected to a second electrode. The firstand second electrodes are coupled to electrode posts, which areconnected to wires 69 (FIG. 3) coupled to a voltage source. When avoltage is applied to the first and second electrodes, a pressure iscreated upon the dielectric film, causing the film to become thinner andto spread outward. By spreading outward, the first diaphragm moves theclamp 66 away from the moveable wall 46 of the pump chamber 44. When theapplied voltage is removed, the film returns to its original shape,causing the clamp to move to its previous position with the aid of abiasing force from the second diaphragm 62. In this way, fluid movementin the fluid passageway is regulated by the pump with cyclicalapplication and removal of power to the first diaphragm. Advantageously,power is conserved because power is not consumed continuously by thepump.

In another embodiment, the second diaphragm 62 is similar to the firstdiaphragm 60 in that it too has an elastomeric dielectric polymer filmdisposed between a pair of expandable conductive coatings. However, thesecond diaphragm is arranged such that when a voltage is applied to thepair of expandable conductive coatings of the second diaphragm, thedielectric polymer film spreads outward, moving the clamp 66 toward themoveable wall 46 of the pump chamber 44. When the applied voltage isremoved, the dielectric polymer film returns to its original shape,causing the clamp to move to its previous position with the aid of abiasing force from the first diaphragm. Thus, fluid movement in thefluid passageway is regulated by the pump of this embodiment withcyclical power supplied to the first diaphragm out of phase withcyclical power supplied to the second diaphragm. With this arrangement,there is greater displacement of the moveable wall and thus, greaterfluid movement relative to powering the first diaphragm alone.

In an alternative embodiment not shown, the pump driver comprises apiezoelectric device coupled to the moveable wall 46 of the pump chamber44. The piezoelectric device is configured to move the moveable wall inresponse to a voltage applied to the device. Piezoelectric devices usedfor pumping fluids are well known in the art and, thus, require nofurther description here.

Referring again to FIG. 2, the variably adjustable valve 42 includes acylindrical valve member 70 extending across the fluid passageway 22.The variably adjustable valve 42 regulates fluid movement in the fluidpassageway based on the position of the valve member, which has a fluidcontacting portion 72 and a threaded portion 74. The fluid contactingportion has an outer surface with a groove 76 extending in a helicalmanner around and along a length of the valve member. The groove has awidth and a depth that varies along the length of the groove. Near oneend of the groove, the groove has a maximum width and a maximum depth.The width and the depth decrease toward an opposite end of the groove.Fluid is completely blocked when the valve member is positioned suchthat fluid contacts a section 78 of the fluid contacting portion havingno groove. Fluid movement corresponding to the unrestricted flow valuemay occur when the valve member is positioned such that fluid passesthrough a section 80 of the fluid contacting portion in which the groovehas the maximum width and the maximum depth.

The position of the cylindrical valve member 70 is controlled by arestrictor driver 82 coupled to the threaded portion of the valvemember. Not shown are a motor and a gear in the restrictor driver, whichadjusts the position of the valve member when power is applied to themotor. The position of the valve member may also be controlled by a knob84 which is sized and shaped to allow a user of the system 20 tomanually adjust fluid movement. The knob functions as a user inputdevice, allowing the user to adjust fluid movement in the fluidpassageway to a desired or target flow value. In one embodiment, theknob is coupled directly to the valve member so that rotation of theknob results in a corresponding movement of the valve member. In anotherembodiment, the knob is coupled to the controller 30, described furtherbelow, such that rotation of the knob results in a change in powersupplied to the motor of the pump driver or a change in the powersupplied to the pump driver.

In FIG. 6 there is shown a flow detector 28 configured to produce anddetect a thermal change in fluid in the fluid passageway 22 and toprovide a detector signal representative of an existing fluid flow valuein the fluid passageway. The flow detector 28 comprises a heat source86, a light source 88, and a light detector 90, each of which aredisposed outside an internal volume 92 of the fluid passageway 22. Theheat source is disposed closest the pump outlet 48 (FIG. 2) and upstreamfrom the light source. The heat source is adapted to heat fluid locatedat a heating region 94 in the fluid passageway. The light source isadapted to produce an interrogating light directed toward fluid locatedat an interrogating region 96 in the fluid passageway. The lightdetector is adapted to provide a detector signal representative of fluidmovement.

In the illustrated embodiment, the heat source 86 is an optical devicethat comprises an first optical lens 98 disposed on a wall of the fluidpassageway 22 and a first laser device 100 in optical contact with thefirst optical lens. The first laser device produces an amplified beam oflight that is directed by the first optical lens 98 to the heatingregion 94 in the fluid passageway. The light has a wavelength and energylevel selected to heat fluid in the heating region 94, thereby producinga thermal change or marker in a portion of a fluid stream travelingthrough the fluid passageway. It will be appreciated that other types ofheat sources, including non-optical devices, may be employed to producethe thermal marker.

Still referring to FIG. 6, the light source 88 comprises an secondoptical lens 102 disposed on a wall of the fluid passageway 22 and asecond laser device 104 in optical contact with the second optical lens.The second laser device produces an interrogating light that is directedby the second optical lens 102 to the interrogating region 96 in thefluid passageway. The interrogating light has a wavelength and energylevel selected so as to prevent or minimize heating of fluid in theinterrogating region.

The light detector 90 comprises an optical waveguide 106 disposed on awall of the fluid passageway 22 and a photodiode 108 in optical contactwith the waveguide. The photodiode is adapted to detect opticalcharacteristics of the fluid in the interrogating region 96, and todetect changes in the optical characteristics when the heated fluid fromthe heating region 94 enters the interrogating region. With thisarrangement, a detector signal produced by the light detector mayrepresent a time period in which the thermal change travels apredetermined distance that separates the heating region and theinterrogating region. The predetermined distance corresponds to apredetermined volume of a portion of the fluid passageway. Thus, it willbe appreciated that the flow detector 28 provides a direct andnon-invasive measurement of flow rate in terms of volume per timeperiod.

Referring again to FIG. 2, a controller 30 is in communication with thepump driver 58, the restrictor driver 82, and the flow detector 28. Thecontroller is also in communication with a display screen 110, which maybe used to indicate an existing flow value of fluid movement in thefluid passageway 22. As discussed in greater detail below, thecontroller receives a detector signal from the flow detector 28. Basedon the detector signal, the controller produces to a pump signal and arestrictor signal to adjust the existing flow value to a desired ortarget flow value, and to automatically maintain the existing flow valueat the target flow value. The pump signal results in the application andremoval of power to electrically activated elements of the pump driver,such as the first diaphragm 60 or a piezoelectric device. The restrictorsignal results in the application and removal of power to the motor ofthe pump driver.

In FIG. 7 there is shown another embodiment of a system 20 in accordancewith the present invention. The system comprises a reusable assembly 112and a disposable assembly 114. The reusable and disposable assembliesare configured to be removably connected to each other. The assembliesare shown detached from each other. Not shown is a means for connectingthe assemblies that includes an electrical connector and mechanicalconnector. The electrical and mechanical connectors may be combined inan electromechanical connector. It will be appreciated that electrical,mechanical, and electromechanical connectors are well known in the artand, thus, require no further description here.

In use, the fluid contacting elements of the system 20 are discardedafter administration of medical fluid to a patient is completed.Elements of the system that are not contaminated by the medical fluidare retained for future use in order to reduce medical costs. In theillustrated embodiment, the disposable assembly 114 includes the fluidpassageway 22, the pump 40, the variably adjustable valve 42, the flowdetector 28, and a manual adjustment device 118 in the form of a smallknob sized to be manipulated by a user. The small knob is connected tothe valve member 70 and allows the user to adjust the existing flowvalue manually after the reusable assembly has been detached. Thereusable assembly 112 includes the controller 30, the display 110, theknob 84, and a power source 116. In this case, the power sourcecomprises a plurality of load cells, which supply power to electricaldevices on both the reusable and disposable assemblies. Thus, when thereusable assembly is detached, the pump and the variably adjustablevalve lose power. Even without power, fluid movement up to theunrestricted flow value is possible.

Referring next to FIG. 8 showing a further embodiment in accordance withthe present invention, a system 20 includes a primary fluid inlet 36 anda secondary fluid inlet 119. Although not shown, the primary fluid inletand the secondary fluid inlet lead to a Y-shaped conduit that is part ofthe fluid passageway 22. With this arrangement, fluids from the primaryand secondary fluid inlets are simultaneously drawn into the pumpchamber 44. User input buttons 117 are provided to allow a user torespond to information shown on the display 110.

Turning now to FIG. 9 in which is shown an embodiment of a method inaccordance with aspects of the invention. Although the method will bedescribed in terms of the systems of FIGS. 1, 2 and 7, it will beappreciated that other systems may be used to implement the method. Atarget flow value is obtained 120 when a user manipulates a user inputdevice. Fluid movement is measured 122 in the fluid passageway by a flowdetector, which supplies a detector signal to a controller. Thecontroller determines 124, based at least on the detector signal,whether the measured fluid movement is substantially equivalent to orcorresponds to the target flow value. If yes, no change is made to theoperational status of a first flow regulator, such as a pump, or to theoperational status of a second flow regulator, such as a variablyadjustable valve. The process is then repeated beginning with anothermeasurement 122 of fluid movement.

Still referring to FIG. 9, if at 124 the measured fluid movement doesnot correspond to the target flow value, the controller determines 126whether the target value is greater than an unrestricted flow value. Ifyes, a change 128 is made to the operational status of the first flowregulator. This change in operational status may, for example, involvethe controller producing a pump signal that incrementally increases ordecreases power supplied to a pump driver. If at 126 the target value isless than or equal to the unrestricted flow value, a change 130 is madeto the operational status of the second flow regulator. This change inoperational status may, for example, involve the controller producing arestrictor signal that actuates a restrictor driver in order to move avalve member in an incrementally more open or more closed position. Theprocess of making an incremental change to the operational status of thefirst flow regulator or the second flow regulator is repeated beginningwith another measurement 122 of fluid movement until the fluid movementcorresponds to the target flow value.

By repeating the process with another measurement 122 of fluid, it willbe appreciated that the system 20 is configured to adjust the existingflow value when the existing flow value strays from the target value forany reason. For example, a change 132 in the amount of fluid in amedicament container may cause the existing flow value to decrease. Sucha change in the amount of fluid may occur during the normal course ofadministration of fluid to a patient or when a near empty medicamentcontainer is replaced with a full medicament container. Also, a change134 in elevation of the medicament container relative to an outlet of anadministration tube may cause the existing flow value to stray from thetarget value.

The change in relative elevation of the medicament container may occurmay when a patient is being moved in such a way that the medicamentcontainer is lowered toward the patient, which may result in a decreasein pressure head at the administration tube outlet connected to thepatient and, thus, a decrease in fluid movement. The change in elevationmay also occur when a patient stands up from a sitting position, whichmay result in an increase in pressure head at the administration tubeoutlet and, thus, an increase in fluid movement. In any event, a changewill be made by the controller to the operational status of the firstflow regulator or the second flow regulator in order to maintain theexisting flow value at the target flow value.

Referring now to FIG. 10, there is shown another method in accordancewith aspects of the invention wherein the unrestricted flow value is notbe predetermined. A target flow value is obtained 136 and fluid movementis measured 138. The controller then determines 140 whether the measuredfluid movement is substantially equal to or corresponds to the targetflow value. If yes, no change is made to the operational status of thefirst flow regulator or the second flow regulator, and the process isrepeated beginning with another measurement 136 of fluid movement.

If at 140 the measured fluid movement does not correspond to the targetflow value, the controller determines 142 whether the fluid movement isless than the target value. If yes, the controller determines 144whether the second flow regulator is at a fully open position. If yes,the controller infers that the target flow value is greater than theunrestricted flow value and instructs the first flow regulator inincrementally increase 146 pumping slightly. This process of increasingpumping activity incrementally is repeated until the fluid movementcorresponds to the target flow value.

If instead at 144 the first flow regulator is not in a fully openposition, controller assumes that the target flow value is less than orequal to the unrestricted flow value and instructs the second flowregulator to incrementally move 148 to a slightly more open position.This process of moving the second flow regulator incrementally to a moreopen position is repeated until a fully open position is reached or thefluid movement corresponds to the target flow value, whichever occursfirst. When a fully open position is reached first, the controllerinfers that the target flow value is greater than the unrestricted flowvalue and instructs the first flow regulator to incrementally increase146 pumping activity slightly. This process of increasing pumpingactivity incrementally is repeated until the fluid movement correspondsto the target flow value.

Still referring to FIG. 10, when instead at 142, the fluid movement isgreater than the target value, the controller determines 150 whether thefirst flow regulator 24 is inactive such that, for example, pumpingactivity is at zero. If yes, the controller 30 infers that the targetflow value is less than or equal to the unrestricted flow value andinstructs the second flow regulator 26 to incrementally move 152 to aslightly more closed position. This process of moving the second flowregulator incrementally to a more closed position is repeated until thefluid movement corresponds to the target flow value.

If at 150, the first flow regulator is active such that, for example,pumping activity is non-zero, the controller assumes that the targetflow value is greater than the unrestricted flow value and instructs thefirst flow regulator to incrementally decrease 154 pumping activityslightly. This process of decreasing pumping activity incrementally isrepeated until pumping activity reaches zero or the fluid movementcorresponds to the target flow value, whichever occurs first. Whenpumping activity reaches zero first, controller infers that the targetflow value is less than the unrestricted flow value and instructs thesecond flow regulator to incrementally move 152 to a slightly moreclosed position. This process of moving the second flow regulatorincrementally to a more closed position is repeated until the fluidmovement corresponds to the target flow value.

In a further embodiment, the reusable assembly 112 (FIG. 7) includes abi-directional communication device 31 for communicating data via wiredor wireless means with a computer 156 shown symbolically in block form.The communication device may be a detachable module electromechanicallyconnected to the controller or it may be an integral part of thereusable assembly. The computer provides the controller 30 with drugdelivery data from a hospital information system 158, shown symbolicallyin block form, to assist the user in administering the right drug to theright patient at the right dose and via the right administration route.Such data received by the reusable assembly may include a drug name anda prescribed infusion rate. Data transmitted from the reusable assemblyto the computer may include a target flow value programmed into thereusable assembly by a user and measurements of fluid movement takenduring the course of infusion. In this way, an alert may be shown on thedisplay 110 of the reusable assembly, or elsewhere on the hospitalinformation system, when the target flow value entered by the user doesnot correspond to the prescribed infusion rate. With the communicationdevice, medical records kept by the hospital information system may beautomatically updated continuously or periodically during the course ofinfusion.

While several particular forms of the invention have been illustratedand described, it will also be apparent that various modifications canbe made without departing from the scope of the invention. It is alsocontemplated that various combinations or subcombinations of thespecific features and aspects of the disclosed embodiments can becombined with or substituted for one another in order to form varyingmodes of the invention. Accordingly, it is not intended that theinvention be limited, except as by the appended claims.

I claim:
 1. A fluid assembly comprising: a fluid passageway comprising aprimary inlet, a secondary inlet, and an outlet, wherein unrestrictedmovement of fluid through the fluid passageway corresponds to anunrestricted flow value; a pump, connected between the primary inlet andthe outlet, configured to permit a fluid movement through the fluidpassageway and to operate when connected to a power source; a valveconnected between the pump and the outlet and configured to restrict thefluid movement through the fluid passageway; and a flow detectorconnected between the pump and the valve and configured to measure thefluid movement.
 2. The fluid assembly of claim 1, wherein the pumpcomprises: a pump chamber, the pump chamber disposed in the fluidpassageway and configured for one-way fluid flow in a direction from theinlet to the outlet of the fluid passageway; a moveable wall; and a pumpdriver coupled to the moveable wall, the pump driver comprising a firstdiaphragm and a second diaphragm, the first diaphragm and the seconddiaphragm coupled together by a clamp such that the first and seconddiaphragms exert a biasing force on the other, the first diaphragmconfigured to expand and move the clamp away from the moveable wall inresponse to a first applied voltage, the second diaphragm configured toexpand and move the clamp towards the moveable wall in response to asecond applied voltage.
 3. The fluid assembly of claim 2, wherein thefirst diaphragm comprises a first elastomeric dielectric film having afirst side and a second side, the first side of the first elastomericdielectric film coated with a first expandable conductive film connectedto a first electrode, the second side of the first elastomericdielectric film coated with a second expandable conductive filmconnected to a second electrode, and wherein the second diaphragmcomprises a second elastomeric dielectric film having a first side and asecond side, the first side of the second elastomeric dielectric filmcoated with a third expandable conductive film connected to a thirdelectrode, the second side of the second elastomeric dielectric filmcoated with a fourth expandable conductive film connected to a fourthelectrode.
 4. The fluid assembly of claim 2, wherein the pump chamberincludes a first check valve configured to allow the fluid movement intothe pump chamber and a second check valve configured to allow the fluidmovement out of the pump chamber.
 5. The fluid assembly of claim 2,wherein moving the clamp away from the moveable wall increases a volumeof the pump chamber, and moving the clamp towards the moveable walldecreases the volume of the pump chamber.
 6. The fluid assembly of claim1, wherein the flow detector comprises: a heat source disposed outsidethe internal volume of the fluid passageway and adapted to heat fluidlocated at a heating region in the fluid passageway; a light sourcedisposed outside the internal volume of the fluid passageway and adaptedto produce an interrogating light directed toward fluid located at aninterrogating region in the fluid passageway; a light detector disposedoutside the internal volume of the fluid passageway and adapted todetect optical characteristics of the fluid in the interrogating region,and to detect changes in the optical characteristics when the heatedfluid from the heating region enters the interrogating region.
 7. Asystem comprising: a first assembly comprising: a fluid passagewaycomprising an inlet and an outlet, wherein unrestricted movement offluid through the fluid passageway corresponds to an unrestricted flowvalue; a pump connected between the inlet and the outlet and configuredto permit a fluid movement through the fluid passageway; a valveconnected between the pump and the outlet and configured to restrict thefluid movement through the fluid passageway; and a flow detectorconnected between the pump and the valve and configured to measure thefluid movement; and a second assembly comprising: a controller coupledto the pump and the flow detector; and a display.
 8. The system of claim7, wherein the valve further comprises a manual adjustment deviceconfigured to adjust the valve.
 9. The system of claim 8, wherein thesecond assembly further comprises a knob configured to couple to themanual adjustment device.
 10. The system of claim 7, wherein the secondassembly further comprises a knob coupled to the controller andconfigured to adjust the valve.
 11. The system of claim 7, wherein thesecond assembly further comprises a power source.
 12. The system ofclaim 11, wherein the power source is coupled to the pump.
 13. Thesystem of claim 7, wherein the second assembly further comprises awireless communication device coupled to the controller.
 14. The systemof claim 7, wherein the second assembly is configured to detach from thefirst assembly.
 15. A method comprising: obtaining a target flow value;moving fluid through a disposable assembly comprising a fluid passagewayand a flow regulating apparatus, the fluid passageway comprising aninlet, an outlet, and an internal volume through which unrestrictedmovement of the fluid corresponds to an unrestricted flow value, theflow regulating apparatus comprising a first flow regulator and a secondflow regulator, the flow regulating apparatus between the inlet and theoutlet; taking a measurement of fluid movement in the fluid passageway;and adjusting a pump rate when the fluid movement does not correspond tothe target flow value.
 16. The method of claim 15, wherein adjusting apump rate further comprises changing the operational status of the firstflow regulator when the target flow value is greater than theunrestricted flow value.
 17. The method of claim 15, wherein adjusting apump rate further comprises changing the operational status of thesecond flow regulator when the target flow value is less than theunrestricted flow value.
 18. The method of claim 15, further comprisingadjusting the pump rate when a change in an amount of fluid in amedicament container connected to the fluid passageway is detected. 19.The method of claim 15, further comprising adjusting the pump rate whena change in a relative elevation of a medicament container connected tothe fluid passageway with respect to an outlet of an administration tubeconnected to the outlet is detected.
 20. The method of claim 15, whereinobtaining a target flow value further comprises receiving a user input.